[PATCH v7 5/5] clk: dt: Introduce binding for critical clock support
From: Maxime Ripard <hidden>
Date: 2015-07-27 07:10:58
Also in:
linux-devicetree, lkml
Hi Lee, On Wed, Jul 22, 2015 at 02:04:15PM +0100, Lee Jones wrote:
quoted hunk ↗ jump to hunk
Signed-off-by: Lee Jones <redacted> --- .../devicetree/bindings/clock/clock-bindings.txt | 39 ++++++++++++++++++++++ 1 file changed, 39 insertions(+)diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index 06fc6d5..4137034 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt@@ -44,6 +44,45 @@ For example: clocks by index. The names should reflect the clock output signal names for the device. +critical-clock: Some hardware contains bunches of clocks which, in normal + circumstances, must never be turned off. If drivers a) fail to + obtain a reference to any of these or b) give up a previously + obtained reference during suspend, it is possible that some + Operating Systems might attempt to disable them to save power. + If this happens a platform can fail irrecoverably as a result. + Usually the only way to recover from these failures is to + reboot. + + To avoid either of these two scenarios from catastrophically + disabling an otherwise perfectly healthy running system, + clocks can be identified as 'critical' using this property from + inside a clocksource's node. + + This property is not to be abused. It is only to be used to + protect platforms from being crippled by gated clocks, NOT as a + convenience function to avoid using the framework correctly + inside device drivers. + + Expected values are hardware clock indices. If the + clock-indices property (see below) is used, then supplied + values must correspond to one of the listed identifiers. + Using the clock-indices example below, hardware clock <2> + is missing, therefore it is considered invalid to then + list clock <2> as a critical clock.
I think we should also consider having it simply as a boolean. Using indices for clocks that don't have any (for example because it only provides a single clock) seem to not really make much sense. Also, since you can have a bunch of them, using critical-clocks seem more appropriate. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150727/752ad1cd/attachment.sig>